Mantle Convection, Faults, Volcanism and Earth's Dynamics

Earth's Internal Heat and Convection Movements

The heat accumulated inside the Earth causes convection movements.

Density relates to temperature: heat reduces density; heat and density vary quantitatively.

Fractures and Diaclases

Diaclases are brittle deformations or cracks in materials, with dimensions on the order of millimeters.

Faults and Block Displacement

Faults are deformations of brittle materials where blocks are displaced. Fault types include the following:

Hanging Wall and Fault Motion

In reverse (inverse) faults, the hanging wall moves upward relative to the footwall and is tilted toward the uplifted block. In normal faults, the hanging wall moves downward relative to the footwall.

Convection Currents in Fluids

Movements consist of convection currents moving up and down inside a fluid. When a fluid becomes unstable due to temperature differences, convection forms.

How Mantle Convection Manifests at the Surface

Convective movements within the Earth's interior are manifested in several ways:

• Terrestrial magnetism: originates in the vigorous convection currents that stir the liquid iron of the outer core.
• Movement of continents: results from convective motions occurring in the Earth's mantle (plate tectonics).
• Volcanism: heat transported from the base of the mantle toward shallower regions gives rise to active volcanic features on the planet, such as oceanic ridges.
• Seismicity: the movements of continents and oceanic plates produce large stresses in the lithosphere; movement of different blocks generates strong earthquakes.
• Segregation of materials: as mantle materials move, density contrasts cause less-dense materials to be transported toward the surface where they are difficult to sink again.

Plumes, Solifluction and Subduction

Thermal plumes are columns of hot mantle material rising from the base of the mantle toward the surface; they cause zones of intense volcanism known as hotspots.

Solifluction (solid flow) describes the behavior of apparently solid material that can flow very slowly like a viscous fluid.

Subduction is the downward motion of oceanic lithosphere; it is part of the convective circulation of the mantle formed by descending slabs of oceanic lithosphere.

Folds: Anticlines and Synclines

Type (fold):

• Anticline — older layers are folded so that they form the core of the fold and are surrounded by younger (more modern) layers.
• Syncline — the youngest (most modern) layers occupy the core of the fold and are surrounded by older layers.

Fault Types (Detailed)

(Fall)

• Normal (direct) — the hanging wall has moved down along the fault plane relative to the footwall.
• Reverse — the hanging wall has moved up; the fault plane is tilted toward the uplifted block.
• Transform — motion is predominantly horizontal, with blocks sliding past each other.

Gaia Theory and the Biosphere

The Gaia Theory proposes that the biosphere — all living beings taken together — behaves as an entity capable of self-regulating physical characteristics and other environmental parameters to adapt the global environment to its needs.